With the blooming of the machine tool industry, the machining accuracy while processing the work piece is improved as well. However, during machining the work piece, the machining accuracy is affected due to the temperature raising occurred in a feed screw driving unit or other driving mechanisms.
For reducing the influence from the temperature during machining, lots of temperature compensating methods such as neural system compensating method, fuzzy control method and linear regression analysis are disclosed to compensate the driving or feeding mechanism of the machine tool or system. In those conventional ways, it is necessary to rely on a temperature sensor combined with a laser positioning device to compensate the machining status according to the temperature variation.
Other way such as U.S. Pat. No. 5,623,857 disclosed a method and apparatus for compensating for thermal distortion for machine tool, which detects a temperature change of a machine mechanism that is influenced by a heat source, calculates a temperature change having substantially the same time constant as a time constant of the thermal distortion of the machine tool by using the temperature change detected, and, finally, corrects a machining error on the basis of a thermal distortion that changes in correspondence with the calculated temperature change.
In the foregoing conventional ways, the sensing location is mainly decided as close as possible to approach the feed screw or the moving mechanism coupled to the feed screw. Each sensing apparatus is connected to a controller or an operating unit through wiring arrangement. Therefore, problems of wiring interference and difficulties for arranging wiring will be occurred. Meanwhile, sensing apparatus with wiring arrangement will also limit the location of installation and even affect the result of sensing, which means that the disposing position of the sensing apparatus is difficult to be installed near the location having maximum parameters variation. In addition, wire abrasion and break are also occurred easily while using the wiring for information transmission and, in some occasions, wiring is difficult to be configured on a rotary mechanism, such as a rotary tool holder.